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Abstract

In order to improve the scalability and reduce the traffic of Gnutella-like unstructured peer-to-peer networks, index caching and controlled flooding mechanisms had been an important research topic in recent years. In this chapter the authors will describe and present the current state of the art about index management schemes, interest groups and data clustering for unstructured peer-to-peer networks. Index caching mechanisms are an approach to reducing the traffic of keyword querying. However, the cached indices may incur redundant replications in the whole network, leading to the less efficient use of storage and the increase of traffic. They propose a multiplayer index management scheme that actively diffuses the indices in the network and groups indices according to their request rate. The peers of the group that have indices with higher request rate will be placed in layers that receive queries earlier. Their simulation shows that the proposed approach can keep a high success query rate as well as reduce the flooding size.

Background And Related Work

BitTorrent

BitTorrent is a peer-to-peer communication protocol (Cohen 2002) that can distribute large amounts of data widely without the original distributor incurring the entire costs of hardware, hosting, and bandwidth resources. Instead, when data is distributed using the BitTorrent protocol, each recipient supplies pieces of the data to newer recipients, reducing the cost and burden on any given individual source, providing redundancy against system problems, and reducing dependence on the original distributor.

Blind Search Methods

Most search methods in Gnutella-like peer-to-peer networks can be categorized into blind search methods and informed search methods (Tsoumakos, & Rousseopoulos, 2006). In blind search methods, there is no mechanism to keep the query results, to judge the best query path, or to use some other information to reduce traffic. Blind search confines the nodes to transmit messages to some adjacent nodes instead of all adjacent nodes without using the information of messages or choosing the best path for transmitting. The typical systems include Gnutella, Modified-BFS (Kalogeraki, Gunopulos, & Zeinalipour-Yazti 2002), Random Walks (Lv, Cao, Cohen, Li, & Shenker 2002), and Dynamic Query (Fisk, 2003) (Ripeanu, Foster, & Iamnitchi 2002).

Key Terms in this Chapter

Structured Peer-to-Peer Networks: A peer-to-peer network that employ a consistent protocol such as a distributed hashing function to ensure that any node can efficiently route a search to some peer that has the desired file. The consistent hashing is also used to distribute the file to a peer.

Random Walk: A search algorithm used in a peer-to-peer network where the query will be forwarded up and down the given list until a match is found, the query is aborted, or it reaches the limits of the list.

Dynamic Query: The search technique the Gnutella adopted to reduce traffic overhead and make searches more efficient, where a search reaches only those clients which are likely to have the files and stops as soon as the program has acquired enough search results.

Peer-to-Peer Networks: A network with equal peer nodes that simultaneously function as both clients and servers to the other nodes on the network.